JP2002086774A - Method and equipment for inspecting abnormal contact pressure of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an equipment for detecting uniform contact of a thermal head with a sheet. SOLUTION: Temperature sensors 14a and 14b are arranged at a plurality of positions in the widthwise direction of a platen roller 11 on the back of a thermal head 12 and an equal quantity of energy is imparted to print elements corresponding to the temperature sensor 14b. A test sheet is passed between the thermal head 12 and the platen roller 11 at least to a position corresponding to that print element. Output values from respective temperature sensors 14a and 14b are then compared and the thermal head 12 is inspected for uniform contact with a sheet 17 based on the comparison results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting an abnormal contact pressure of a thermal head used in a thermal printer.

[0002]

2. Description of the Related Art A thermal printer shown in FIG. 3 is an external paper feed type printer. For example, a paper 1 folded in a zigzag pattern is supplied from a paper supply port 3 of a housing 2 to the inside thereof. The paper 1 is set by being inserted along a passage 4 into a printing unit 7 including a platen roller 5 and a thermal head 6 and the like.

On the other hand, in the thermal printer, a large number of printing elements (heating elements) are implanted on the printing surface of the thermal head 6 in the width direction of the paper 1, and energy is applied to necessary printing elements among the printing elements. To generate heat.

In this thermal printer, the paper 1 is moved by a platen roller 5 and printing is performed on the paper by a printing element of a thermal head 6.

[0005]

By the way, in such a thermal printer, when the contact pressure of the thermal head is not uniform at each position in the width direction of the paper, the printing element of the portion where the contact pressure is high is not used. There is a danger that the print element will be worn more than the other parts of the print element, thereby causing disconnection.

The present invention has been made in view of such circumstances, and has as its object to provide a method and apparatus for easily detecting whether or not a thermal head is uniformly in contact with a sheet.

[0007]

In order to achieve the above object, the present invention provides a thermal head contact pressure abnormality inspection method according to the first aspect of the present invention, wherein a plurality of thermal heads are arranged along a direction in which print elements are arranged in the thermal head. Place a temperature sensor in the place,
While applying an equal amount of energy to a printing element corresponding to the temperature sensor, a test sheet is passed between the thermal head and a platen roller at least to a position corresponding to the printing element. It is characterized in that the output values of the sensors are compared and it is checked whether or not the thermal head is in uniform contact with the paper based on the comparison values.

That is, according to the present invention, the printing element of the thermal head is uniformly heated, and the temperature rise when the test paper is brought into contact with the printing element and detected is detected by the temperature sensor. It is inspected whether the contact is uniform.

According to the present invention, since the inspection can be performed by a printing operation which is normally performed, the apparatus can be inexpensive and a stable inspection can be performed over a long period of time.

According to a second aspect of the present invention, there is provided a thermal head contact pressure abnormality inspection apparatus, wherein a plurality of printing elements are arranged, and the thermal head is provided on the thermal head along the arrangement direction of the printing elements. Multiple temperature sensors,
A platen roller that rotates and conveys the test paper while abutting on the thermal head; and an energy supply unit that supplies an equal amount of energy to a printing element corresponding to each of the temperature sensors; The output values of the temperature sensors when the test paper is passed at least to the position corresponding to the printing element between the platen roller and the platen roller are compared, and a difference between the output values is within a set value. It is characterized in that comparing means for judging the difference and outputting an alarm signal when the difference between the output values exceeds a set value, and alarm means for issuing an alarm in accordance with the alarm signal are provided.

According to the present invention, since only the temperature sensor and the test paper are used, the apparatus can be obtained at a low cost, and stable inspection can be performed over a long period with less trouble.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method and an apparatus for inspecting an abnormal contact pressure of a thermal head according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a thermal head contact pressure abnormality inspection apparatus in a thermal printer, and FIG. 2 shows an inspection procedure of the apparatus.

FIG. 1 shows a printing unit 10 of a thermal printer. The printing unit 10 includes a platen roller 11 and a thermal head 12, and a number of printing elements (heating elements) 12a are implanted on the printing surface of the thermal head 12 in the width direction of the paper.

The thermal printer is provided with a thermal head contact pressure abnormality inspection device 13. In this device 13, on the back side of the printing element 12a implanted at an appropriate position in the width direction of the thermal head 12,
Two thermistors 14a and 14b are provided as temperature sensors, and these thermistors 14a and 14b are connected to comparison means 15 such as a comparator. In this apparatus, the comparison stage 15 further includes a buzzer, a lamp, and other alarm means 1.
6 is connected.

Then, the contact pressure abnormality inspection device 13 for the thermal head detects the contact pressure abnormality of the thermal head 12 according to the flow shown in FIG.

First, the inspection device 13 is operated with the test paper 17 set on the printing unit 10 (step 2).
1). The test paper 17 may be a heat-sensitive paper or a white paper as long as it has a smooth surface and a certain degree of hardness and a uniform thickness so as to be suitable for thermal printing. In short, it is only necessary that the thermal head 12 and the platen roller 11 are uniformly pressed against the thermal head 12 when the platen roller 11 is in a normal positional relationship.

Next, at least the printing element 1 corresponding to each of the thermistors 14a and 14b is supplied from the energy supply means 18.
2a is applied with uniform energy (step 2
2). At the same time, the platen roller 11 is driven by the platen roller driving means 19, and the test paper 17 is moved.

Then, the detected values Ta and Tb from the thermistors 14a and 14b are obtained by the comparing means 15 (step 23), and they are compared by the comparing means 15 to determine whether the difference between them is larger than the set value ΔT. Is determined (step 24). If the difference between the detected values Ta and Tb is larger than the set value ΔT, the application of energy to the thermal head 12 is stopped (step 25) and the alarm means 16 is activated (step 26).

The difference between the detected values Ta and Tb is equal to the set value ΔT.
If smaller, the application of energy to the printing element 12a and the driving of the platen roller 11 are continued. Then, for example, by applying a test end signal by operating the printer stop button, the application of energy to each printing element 12a and the driving of the platen roller 11 are ended (step 27), and the inspection is ended (step 2).
8).

In the above embodiment, the set value is a value within a range in which non-uniformity of the contact pressure is allowable, and the magnitude of the energy applied to the printing element 12a, the thermistor 1
The distance is appropriately set in consideration of the distance between 4a and 14b.

In the flow shown in FIG. 2, what is displayed as printing is to perform the same operation as in printing, that is, to apply energy to the printing element 12a, and to drive the platen roller 11. It means things.

Further, a solid print or a test chart may be printed on the surface of the test paper 17, or the white paper may simply be passed. In short, at least the thermistor 14a,
It is sufficient that the energy applied to the printing element 12a corresponding to the portion 14b is uniform.

In the above embodiment, the thermistors 14a and 14b are used as temperature sensors. However, other non-contact type temperature sensors such as thermocouples can be used instead of the thermistors 14a and 14b.

[0025]

As described above, according to the thermal head contact pressure abnormality inspection method according to the present invention, by detecting the temperature with the temperature sensor, the thermal head is applied to the paper in substantially the same procedure as the printing operation. To check whether the contact is even.

That is, according to the present invention, since the inspection can be performed by the printing operation which is usually performed, the apparatus can be inexpensive and stable inspection can be performed for a long period of time.

Further, according to the thermal head contact pressure abnormality inspection apparatus of the present invention, since only the temperature sensor and the test paper are used, the apparatus can be obtained at low cost, and the stable inspection can be performed for a long time with few failures. be able to.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a state in which a contact pressure abnormality inspection device for a thermal head according to the present invention is applied to a thermal printer.

FIG. 2 is a flowchart showing an inspection procedure of the thermal head contact pressure abnormality inspection apparatus of FIG. 1;

FIG. 3 is a conceptual diagram showing a thermal printer to which a method for detecting an abnormal contact pressure of a thermal head according to the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Printing part, 11 ... Platen roller, 12 ... Thermal head, 12a ... Printing element, 13 ... Test device for contact pressure abnormality of thermal head, 14a, 14b ... Temperature sensor (thermistor), 15 ... Comparing means, 16 ... Means, 17: Test paper, 18: Energy supply means, 19: Platen roller driving means

Claims (2)

[Claims] A temperature sensor is provided at a plurality of locations along a direction in which print elements are arranged in a thermal head, and an equal amount of energy is applied to a print element corresponding to the temperature sensor. In the meantime, the test paper is passed through at least the position corresponding to the printing element, and the output values of the temperature sensors obtained at this time are compared. Based on the comparison value, the thermal head uniformly contacts the paper. A method for inspecting an abnormal contact pressure of a thermal head, which inspects whether or not the pressure is on. 2. A thermal head in which a plurality of printing elements are arranged, a plurality of temperature sensors provided on the thermal head along the direction in which the printing elements are arranged, and a plurality of temperature sensors which rotate while being in contact with the thermal head. A platen roller for transporting test paper, and an energy supply unit for supplying an equal amount of energy to a printing element corresponding to each of the temperature sensors, and at least the printing between the thermal head and the platen roller. The output values of the temperature sensors when the test paper is passed through the position corresponding to the element are compared, and it is determined whether or not the difference between the output values is within a set value, and the difference between the output values is determined. A contact means for outputting a warning signal when the pressure exceeds a set value, and a warning means for issuing a warning in accordance with the warning signal. Atmospheric detection device.